That chart is probably overly dramatic (and they conveniently sell tranny coolers), but the fundamentals seems true that you don't want the ATF going beyond about 225°F.
The thermal expansion coefficient of materials is constant, most aluminums being about 12 to 13 ppm (e.g. microinch) per °F and irons are typically about 6 to 7. My main worry would be ruining the fluid more than the marginally worse metal expansion. Joining dissimilar metals is a bad idea but unfortunately common on our junk.
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"Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty. Nobody is able to achieve this completely, but the striving for such achievement is in itself a part of the liberation and a foundation for inner security. " --Albert Einstein
Last edited by DaveInDenver; 05-31-2013 at 08:06 PM.